The overall objective of the proposed research is the identification of genes of Rous sarcoma virus (RSV), a representative RNA tumor virus, responsible for the initiation and maintenance of the transformed state. The functions specified by such genes, as well as replication functions, will be analyzed by the use of conditional-lethal mutants. In addition, emphasis will be placed on determining the role of membrane alterations in the maintenance of transformation. Such studies will include both physiological and biochemical analyses of the phenotypic alterations of the plasma membrane of transformed cells compared with the parental untransformed cells. Aspects of the altered membranes include interaction of the membrane with lectins, cellular morphology, altered transport proteins, altered or differing levels of membrane enzymes, and altered antigenicity. The structure of the virion, including RNA and proteins, will be analyzed to determine if the mutants differ from the wild-type. Finally, it is hoped that it may be possible to investigate control mechanisms, operating at the level of transcription and/or translation, which regulate the synthesis of molecules involved in the maintenance of transformation.